Terebellobranchia hiata ( Treadwell, 1931 ) Londoño-Mesa, 2009

Londoño-Mesa, Mario H., 2009, Terebellidae (Polychaeta: Terebellida) from the Grand Caribbean region 2320, Zootaxa 2320 (1), pp. 1-93 : 66-68

Terebellobranchia hiata ( Treadwell, 1931) comb. nov.

Figures 19 A-J

Terebella hiata, Treadwell, 1931:80–81 .

(Not junior synonym of Polymniella aurantiaca, Hartman, 1956:297 .— Holthe, 1986b:153).

Type material: Holotype: AMNH 3550 Haiti, 1927, Sta. 27289 (no more data).

Additional material: Florida: AMNH 465 (5) Dry Tortugas, Florida, VI-VII.1909 (as Polymniella aurantiaca ). Mexican Caribbean : Quintana Roo State: ECOSUR TERE-22 (1) Ascension Bay, Sian Ka’an (19º37'05.57"N 87º35'33.3"W), VII.2004. Antilles: AMNH 2763 (1) Sand Cay, 5m off shore, North of Bizoton Reef, Haiti, 11.IV.1927. UMML 22.988 (1) North of Martinique Island (14°54'N 61°04'W), R/V “Pillsbury” Sta. 913; 10.VII.1969; 47m. UMML 22.989 (1) North off Antigua (17°18'N 61°52'W), R/V “Pillsbury” Sta. 968; 20.VII.1969; 18m. ZMA V.Pol. 5305 (1) Awa di Oostpunt, Curaçao, Sta. 75-40; 14.IX.1975; Thalassia , 0.6–0.7m. LEB-Te (2) Mochima, Venezuela, 10.III.2002.

Description: Holotype incomplete, with 96 segments, 69mm length, thorax 10mm long, 3mm wide ( Figs 19A,B ). Abdomen 1.6mm wide (last segment 1mm wide). Tentacular membrane reaches upper lip, ventral edges joining those of upper lip; only two short tentacles left ( Figs 19C,D ). Eyespots absent. Upper lip short, semicircular, with ventral edge close to each other. Lower lip flattened, reduced. Fifteen ventral shields ( Fig. 19D ); first shield smooth; next shields well developed, thinner, with some longitudinal wrinkles, decreasing in width, but more swollen posteriorly. Ventral groove from segment 16 to posterior end, deeper on posterior region. Dichotomous branched branchiae on segments 2, 5 and 8, increasing in size posteriorly, last pair twice as long as the first ( Fig. 19E ). Base of second pair of branchiae inserted at the inter-segmental line between segments 4 and 5, but slightly displaced towards segment 5. Third pair inserted at inter-segmental line between segments 7 and 8, slightly displaced towards segment 8. Nine pairs of nephridial papillae from segment 5, between noto- and neuropodia, as swollen rounded structures placed dorsally to tori. Pairs of notopodia along all the body; first 16 pairs of notopodia larger, more swollen, closer to the next. After segment 18, notopodia fused with neuropodia, chaetae emerge from dorsal edge of neuropodia, on thin and long chaetal lobe. Notochaeta of two lenghts; short and long chaetae bilimbate in base, with distal oblique serrated region ( Fig. 19F ). Neuropodia with uncini in single rows ( Figs 19G,H ); then in double rows ( Figs 19I,J ). First pair of neuropodia short, oblique to middle body line, and dorsally more swollen. Then, neuropodia perpendicular after segment 13. All neuropodia swollen and well-developed; last neuropodia less swollen, long. Uncini MF:3–4:3–4:3–4; MF long, and teeth smaller above it; Oc rounded; PP triangular, PF absent; Bs smoothly curved; AP projected, curved downward, AF absent; SrP triangular; SrA absent; USr rounded, almost closed by MF and SrP.

Staining pattern: Tentacles stain only on both sides of the groove; ventral shields and thoracic notopodial glandular tissue stain deeply ( Fig. 19B,D,E ), and nephridial papillae stain circularly with white center. The remaining structures remain pale.

Variations: The non-type specimen from Haiti is complete, in contrast to the holotype; it has 121 segments, notopodia terminating 15 segments before pygidium; it is 71.5mm long, thorax 20mm long, 3mm wide. Other specimens are incomplete. The specimens from North Antigua and from the Mexican Caribbean have small brown eyespots, laterally, on the tentacular membrane. With the exception of the holotype, the other specimens have nephridial papillae on segments 6–10, in the same position .

Discussion: This species is valid. After the description by Treadwell (1931), Hartman (1956) considered this species as invalid, and she included it into Polymniella aurantiaca Verrill, 1900 , from Bermuda. However, she did not include enough information about the segments on which the branchiae and notopodia are present in both species. She referred to a previous publication ( Hartman, 1942) indicating that P. aurantiaca has branchiae on segments 1, 2 and 5. Nevertheless, this information does not match with the description of Polymniella by Verrill (1900), who indicated branchiae were present on segments 2, 3 and 6, first pair of notopodia in the first branchial segment (segment 2). The main differences between Terebellobranchia hiata comb. nov., and P. aurantiaca are that the former has pair of branchiae on segments 2, 5 and 8, and pairs of notopodia from segment 4, and the latter has pairs of branchiae on segments 3, 4 and 7, and pairs of notopodia from segment 4. Herein, Terebellobranchia hiata is not considered as a Polymniella species because of the distribution of the branchiae.

Type locality: Haiti, possibly Sand Cay , north of Bizoton Reefs, because AMNH 2763 (non-type material) was collected there in the same year, and at the same date. Treadwell mentions that this species was collected during the Expedition by the New York Zoological Society to Haiti in 1927 .

Distribution: Florida, USA; Haiti, Curaçao, Martinique and Antigua. Shallow water to 47m.

Figures

FIGURE 19. Terebellobranchia hiata comb. nov., (Holotype AMNH 3550): A. Thoracic region in dorsal view. B. Thoracic region in ventral view. C. Anterior end in dorsal view. D. Anterior end in dorsal view. E. Thoracic region in lateral view. F. Chaetae from segment 11. G. Uncini from segment 5. H. Uncini from segment 6. I. Uncini from segment 11. J. Uncini from segment 31. Scale bars: A,B,E: 1.6mm; C,D: 0.8mm; F: 0.06mm; G-J: 0.03mm.